GUI triggering actions in a separate process

Question

I'm experiencing a problem with python-multiprocessing and Tkinter GUI. I have two processes:

• main, running Tkinter GUI in a loop
• second process to do all other tasks

Here are the things I'm struggling with:

1. I want to trigger an action (f.eg. start a specific task in the second process) by clicking on a GUI button.
2. Then, when user clicks that button and the task in the second process starts, GUI changes the window to a new one (already know how to change windows). In the new one there is also a bunch of buttons, but I want them to be unclickable (or cause nothing when clicked) until the task in 2nd process is finished.

What is the best way to do this?

EDIT: Before I started to use multiprocessing, the code for my button and the triggered function looked like this:

button48g = tk.Button(self, text='48g', height = 10, width = 20, font=("Courier", 20), bg="WHITE", command=lambda: controller.show_frame(GUI.PageOne48g))
button48g.bind('<Button-1>', GUI.commands.leftClick)

where leftClick was a function, f.eg.

def leftClick(event):
    print('Left click!')

Now, the leftClick function is in the other process, called 'test'.

queueTestResults = multiprocessing.Queue()
test = multiprocessing.Process(name='test', target=testProcess, args=(queueTestResults,))
test.start()

gui = GUI.GuiApp()
gui.root.mainloop()

while queueTestResults.empty():
    pass

someResults = queueTestResults.get()
test.join()

Answer 1

Its easier to accomplish with 2 Queues rather than 1 queue in my opinion

q_read,q_write = multiprocessing.Queue(),multiprocessing.Queue()

def slow_function():
    time.sleep(5)
    return "Done Sleeping"

def other_process_mainloop(q_write,q_read):
    # this process must get an inverted order
    while 1: # run forever
       while q_read.empty():
           time.sleep(0.1) # waiting for a message
       message = q_read.get()
       if message == "command":
           q_write.put(slow_function())
       else:
           q_write.put("Unknown Command")

# start our worker bee
P = multiprocessing.Process(name="worker",target=other_process_mainloop,
                                    # note inverted order
                            kwargs={q_write:q_read,q_read:q_write)

now make a helper function to send the command and wait for the response

def send_command(command_string,callback_fn):
    def check_for_response():
       if q_read.empty():
          return gui.after(200, check_for_response)
       callback_fn(q_read.get())

    q_write.put(command)
    gui.after(200,check_for_response)

# now you can just call this method when you want to send a command

def on_button_clicked(event):
    def on_result(result):
        print("Work is Done:",result)
        gui.lbl.configure(text="All Done!! {}".format(result))            

    gui.lbl.configure(text="Doing some work mate!")
    send_command("command",on_result)